Again Pokeys57CNC problems, anyone using it?

[yaakovKatz]

i now plan use it first time with mach 4 with new cnc from china
i already bought all parts and take them with me to china
next month ill be there to test on machine
first question is about stability, i use spindle ,3 axis ,magazine with servo motors ,drill head with 12 tool s on it
i plan use the pokeys57 with 5 relay cards and use all optional inputs
most i fried is from noise and stack machine
second is very strange to me is that there no input for encoders to controller ,that mean even i use servo motors ,the encoder input only to the servo motor driver ,and not any conection to mach4 to see real position
thks
yaakov

[Ger21]

second is very strange to me is that there no input for encoders to controller ,that mean even i use servo motors ,the encoder input only to the servo motor driver ,and not any conection to mach4 to see real position

The only low cost controls that can run in true closed loop are LinuxCNC, and Dynomotions KMotionCNC.

[yaakovKatz]

do you have experience with Dynomotions KMotionCNC?
do you think its batter then mach4?
is it so flexible and can manage like mach4?
thanks alot
yaakov

[kjetor]

think i have read somewhere that pokeys57cnc can use encoders on servo's.. but not sure

[m_c]

As Ger says LinuxCNC and KFlop are the only two reasonably priced options that can handle encoders.
However, unless you're running analogue servos, then there's not really any benefit to feeding back encoders.

The only real benefit of having encoder feedback on a step/dir (or CW/CCW) system, is for tuning, as it allows you to know exactly how the servo is responding to moves. But once the system is tuned, there is no practical difference between the controller stopping things because of following error, or the servo drive disabling things because of a following error.

KMotionCNC itself is pretty basic, but it'll do everything you need to control a CNC machine, and the new screen editor does let you alter quite a lot of things. The source code is also provided for KMotionCNC, so you can even modify it if needed (if you want to use non-simple kinematics, then you need to be able compile the required configuration files)
The real benefit of KFlop is that it is highly configurable, and can be programmed to handle pretty much any configuration of machine with up to 8 axis. And the KMotion configuration software has lots of functionality for tuning servos, along with being able to see encoder/axis positions, In/Out statuses, and a C program editor/compiler for creating the required files to configure the KFlop.

[yaakovKatz]

thanks alot for yours answer
what tuning you mean? and if it necessary is that mean that with mach4 i cant get good tuning?
i thought that benefit is that when motor power of(e-stop ) even if you move axis by hand ,controller know real position
other question is ,with mach4 as i c you can also manage the interface...and many other function
do you think its less then KFlop?
thks
yaakov

[m_c]

Tuning is for helping set axis parameters, I.e acceleration, max speed, following error...

With KMotion, you can carry out test moves, and then show the resultant data in a few different ways, so you can see exactly how the axis is responding. On a closed loop step/dir system, it would help establish the maximum acceleration, before the servo couldn't keep up, as you can see the following error, rather than relying on the servo drive faulting because the following error has been exceeded.
Without access to that kind of information, you've just got rely on establishing tuning figures that work, and hope following error is kept to a minimum. It is worth mentioning that there are plenty machines that run without any accuracy issues, that have solely been setup without any kind of data plotting.

Being able to maintain position is a valid reason, but I'll be honest and say it's something that sounds good to have, but in reality isn't much use. I have that ability on my lathe, but after an E-stop I'll always re-home it anyway just to make sure it's where it thinks it is. The CS-Labs CSMIO-IP/A analogue interface also has this functionality.


I've never used Mach 4, so I have no idea what it can or can't currently do.
KFlop is probably the most powerful and adaptable controller in it's price range, but you have to understand C Programming to make the most of it.
Whereas Mach 4 does most of the controller functions, handles the inputs and outputs, and tells the controller how to respond, KFlop relies on having C programs loaded to it, and will handle the required inputs/outputs internally to complete what KMotionCNC has requested.

A good example would be a tool changer.
Mach 4 will tell the controller when to activate any outputs, will monitor the inputs, and control the tool changer motion directly within Mach 4. A key thing is any response to inputs it reliant on the speed on communication between the controller and Mach 4. I know with Mach 3 this was limited to a 10Hz response speed, but have no idea how fast the scripting runs in Mach 4.
KMotionCNC will rely on a C Program within the KFlop, and simply tell the KFlop to load the required tool. The KFlop will activate any outputs, and monitor the inputs with no further input from KMotionCNC. Response time to any input changes is only limited by the KFlop C Program slice time (you can have up to 7 C programs running, with each given an equal time allocation in sequence), but even with the maximum 7 C programs running, response time is still sub millisecond.

What's suitable for you depends on what you are trying to achieve.